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Selective Uptake and Gas Transport in Chemically Modified PIMs

Satilmis, Bekir

[Thesis]. Manchester, UK: The University of Manchester; 2015.

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Abstract

The research aimed to develop chemically modified PIM-1s for use in adsorption and gas separation processes. In particular, the nitrile group in PIM-1 was converted to several different functional groups to manipulate the interaction ability of PIM-1 with different species.Synthesis of PIM-1 was achieved by two different methods, using both the low (72h, 65 oC) and the high temperature (40 min, 160 oC) methods. Hydrolysis of PIM-1 was performed in the presence of 20 % and 10 % NaOH solutions (1:1 H2O/ethanol) at 120 and 100 oC, respectively. The reaction resulted in a mixture of hydrolysis products. The composition of the polymer has a profound effect on the final performance of the polymer. Powder samples of hydrolysed PIMs were used in the research. The reduction of nitrile to primary amine was achieved using borane dimethyl sulphide complex, resulting in amine PIM-1. Both membrane and powder forms of amine PIMs were studied. The reaction of PIM-1 with ethanolamine and diethanolamine produced hydroxyalkylaminoalkylamide PIMs. The combination of all available techniques (ATR-IR, solution and solid state NMR, TGA, Elemental analysis, UV, GPC, MALDI-ToF, low pressure N2 sorption) was used to characterise the polymers.Gas sorption studies of modified PIMs showed that the sorption capacities of polymer altered depend on the modification. Hydrolysed PIMs showed reduced CO2 uptake. Ethanolamine modified PIM showed reduced CO2 uptake along with even more reduced N2 uptake, leading to enhanced CO2/N2 ideal selectivity at 1 bar. Amine modification increased the CO2 uptake of the polymer, while showing the same N2 uptake. Enhanced sorption selectivity was also achieved by amine PIM-1.Although chemical modifications reduced the permeability of the membranes, enhanced gas selectivity was obtained. Enhanced H2/CO2 selectivity placed amine PIM-1 above the 2008 Robeson upper bound. The relationship between the degree of conversion and permeability of amine PIM-1 was studied in detail. The effect of temperature and pressure on the permeability of amine PIM was studied, using several different temperatures and pressures. Ethanolamine modified PIM showed size selective behaviour by enhanced H2/N2 and H2/CH4 selectivities, and it crossed the 2008 Robeson upper bounds.Dye adsorption studies revealed that chemical modification manipulated the interaction ability of PIM-1. PIM-1 showed high affinity for neutral dye. While hydrolysed PIMs showed high affinity for cationic species, amine and ethanolamine modified PIMs displayed high affinity for anionic dyes. The factors affecting the uptake capacity of PIM-1, including temperature and pH, were studied along with kinetics of dye adsorption.Thermal treatments of modified PIMs and their structural characterisation were performed. The adsorption and separation performances of thermally treated and untreated modified PIMs were compared.